1. Field of the Invention
This invention relates to devices used to combine or mix dry solid constituents into a homogeneous mixture, and more particularly, it relates to a blender for continuously and uniformly distributing a flow of dispersed solids into a flow of another solids to produce a flow of homogeneous solids.
2. Description of Prior Art
Various types of blenders or mixers have been proposed to effect the mixing of solids within solids. For example, many of these devices are operable only on batches of materials. In this case, different solids are placed within a container and therein agitated by paddles, tumbling, or the like, until a one solid is dispersed within the other. These systems are unsatisfactory in that they are a batch operation and useful only with solids having similar densities and other properties which does not detract from the batch type mixing or blending effort. It would be preferable to employ devices for effective distribution continuously of one solid within another solid. However, present mixing systems are not ameniable to producing the distribution uniformly of a first solids amount into second solids in a one pass, continuous flow, low mixing energy mode of operation.
There is a special need in present day, high volume plastic molding operations to supply a homogeneous mixture of plastic pellets containing very small amounts of particulate colorant, mold release agents, slip mortar batch and like additives, which additives usually are not present in amounts more than a 0.1% by weight. It is common practice in the plastics industry for the supplier of custom blended plastic materials to provide railroad car lots of plastic blends to the molder or fabricator of the plastic products. The custom plastic supplier usually secures a large amount of the bulk plastic solids in the form of small pellets in railroad car lots of approximately 180,000 pounds. This bulk plastic solids is presently removed from its shipping containers. Then, the small amounts of colorant, release agent (and other materials) are mixed into the plastic pellets in lots of about 10,000 pounds to produced the desired plastic blends. However, this blending operation has been found to basically involve either high sheer-types of recirculating flows or a multiplicity of batch type operations within mixing vessels. None of these mixing or blending systems is satisfactory because of being time consuming, subjecting the plastic pellets to a high sheer/mechanical abrasion environment which causes melting, dusts or other damage to the plastic pellets.
It would be greatly advantageous to have a system where a flow of the first solids (e.g., additive) is directly and continuously mixed into a flow of the second solids (e.g., plastic pellets) in a single pass between one bulk container and the resultant homogeneous blend of solids is loaded into a suitable hopper, such as a railroad car for shipment directly to the ultimate user. Stated in another manner, the preferred blending system is capable of producing continuously a homogeneous solids flow at a great volume in a single blending stage by the uniform dispersion of a fixed proportion of the dispersed first solids, such as colorant, mold release agent, slip master batch and the like, within a second solids without subjecting the constituents to high sheer or abrasive conditions.